MODs- wait for "break in" or not?

[MauiCruzer]

Is it better to "open up" a muffler when the saw is new, or is it better to wait after the engine "breaks in". Once the saw is opened up, how do you know if your carb is set to the proper "richness". I opened up my 338 cali with great results after the engine was broken in. The saw now screams, with the carb set to 4-cycle opened up (once the carb limit-caps were pulled off) There were no problems with the high setting, but if the low is set on the rich side, the saw looses its acceleration snap.My second question is, how do know if you modified saws carb is set to lean? Thanks

 

[NWCS]

any mod work WILL require the carb to be retuned. with the extra air flow it will be lean.. very likley to a saw murdering extent. tuning method about the same as a stock saw. set it till it runs good and starts 4stroking on the high end. i really dont think it matters if the saw is broke in or not. as long as you stick to a good break in method either way. my husky 288 was heavily muffler modded with a brand new piston and rings and did great. i usually run my saws a tad rich over the normal since they get used hard with VERY agressive chain.

 

[HiOctane]

Aside warranty consideration,if the saw is brand new,you can open the muffler w/o problems i think.You gonna know if the saw is too lean at hi speed when you cut wood and the saw does like she is losing rpm when cutting.Stop cutting and open hi speed adj a bit and try back until she is close to 4 stroking at hi rpm while cutting.Its more difficult to explain than doing it right on the saw but you should succeed.

 

[DirtTroll]

I do it from the get go, but I rebuild my own saws and could care less about the worthless warrenty.